Coke Plant Wastewater Posttreatment by Fenton and Electro-Fenton Processes

After conventional biological treatment processes, effluents of the coking industry contain high concentration of nonbiodegradable and refractory organic matters, which should be treated to satisfy the discharge water quality standards (chemical oxygen demand [COD] < 150 mg/L, NH3-N< 25 mg/L). In this study, post-treatment of coke plant wastewater was treated by the direct Fenton and anodic electro-Fenton (EF-Feox) methods. COD and total organic carbon (TOC) values were selected as the target parameters. COD and TOC removal efficiency was investigated through changing some operating parameters such as initial pH, initial H2O2 concentration, and current density. Under the optimum operating conditions of each progress, COD and TOC were removed more efficiently in the EF-Feox system (90% and 84.4%) compared with that in the Fenton method (61.96% and 48.12%). Influence of H2O2 feeding on removal efficiency was also investigated in this study. Results indicated that gradual addition of H2O2 instead of initial addition was a simple and convenient means of removing COD and TOC effectively. Furthermore, settling characteristics of waste sludge under different operating conditions was studied. In general, the EF-Feox process can be a promising and reasonable method in the post-treatment of coking wastewater.